Arterial pressure in the intensive care unit: physiological models

Abstract

For cardiovascular care in the intensive care unit (ICU), it may be useful to apply simple physiological equations. Mean blood pressure is constant from aorta to peripheral large arteries, and this allows calculating total arterial resistance, arterial elastance, and left ventricular work and power. Both systolic and pulse pressure are physiologically amplified from aorta to periphery. However, simple physiological models help explain why respiratory variations in peripheral pulse pressure precisely quantify the amount of cardiac preload in reserve in numerous ICU patients. The recent development of arterial tonometry may allow the non-invasive assessment of aortic compliance, time constant of the aortic Windkessel, cardiac output, and myocardial oxygen supply/demand ratio. The role of pressure wave reflection in the build-up of aortic pressure is still debated. Several studies have consistently documented that the second systolic peak of radial artery pressure matches the systolic aortic pressure, and this could be explained by new pressure propagation models rather than by classic models, a point that deserves further studies.